#include <iostream>
int operacion (int n1, int n2);
using namespace std;
int main()
{
    int n1;
    int n2;


    cin>>n1;
    cin>>n2;

    cout<<operacion(n1, n2);

    return 1;
}

int operacion (int n1, int n2)
{
   int suma;
   suma=0;

   while (n1<=n2)
   {
       suma=suma+n1;
       n1++;
   }

   return suma;
}

